Seasonal Variation in Parental Satisfaction With Pediatric Orthopaedics.

BACKGROUND: The degree of parental satisfaction with health care is determined by the family's characteristics and expectations. Many aspects of human physiology and behavior have seasonal rhythms. The purpose of the present study was to determine whether parental satisfaction scores vary across the year in a pediatric orthopaedic outpatient population. METHODS: We retrospectively reviewed a total of 22,951 parental satisfaction scores related to outpatient pediatric orthopaedic encounters between October 2015 and April 2019. Parental satisfaction was measured using the provider subdomain of the shortened version of the Hospital Consumer Assessment of Healthcare Providers and Systems (HCAHPS). Families were stratified according to various pediatric orthopaedic subspecialty services. RESULTS: The satisfaction scores of all pediatric orthopaedic encounters combined did not vary significantly across the year (P=0.8745). When the families were stratified into groups by pediatric orthopaedic subspecialty clinic, variation in seasons was not associated with statistically significant variation in satisfaction scores for the elective surgery, sports medicine, trauma/fracture care, and hand/upper extremity services. However, satisfaction with the spine service was significantly lower in the winter compared with the summer and fall (73.9±3.8 vs. 83.5±5.3 and 82.6±3.6, respectively; P=0.0147). CONCLUSIONS: The provision of pediatric spine care in a region with 4 distinct seasons received lower parental satisfaction scores during the winter than during the summer and fall. This seasonal variation is an additional source of bias in the measurement of satisfaction with health care. LEVEL OF EVIDENCE: Level II-retrospective study.

Anatomic is better than isometric posterior cruciate ligament tunnel placement based upon in vivo simulation.

PURPOSE: To elucidate the effects of various tibial and femoral attachment locations on the theoretical length changes and isometry of PCL grafts in healthy knees during in vivo weightbearing motion. METHODS: The intact knees of 14 patients were imaged using a combined magnetic resonance and dual fluoroscopic imaging technique while the patient performed a quasi-static lunge (0°-120° of flexion). The theoretical end-to-end distances of the 3-dimensional wrapping paths between 165 femoral attachments, including the anatomic anterolateral bundle (ALB), central attachment and posteromedial bundle (PMB) of the PCL, connected to an anterolateral, central, and posteromedial tibial attachment were simulated and measured. A descriptive heatmap was created to demonstrate the length changes on the medial condyle and formal comparisons were made between the length changes of the anatomic PCL and most isometric grafts. RESULTS: The most isometric graft, with approximately 3% length change between 0° and 120° of flexion, was located proximal to the anatomic femoral PCL attachments. Grafts with femoral attachments proximal to the isometric zone decreased in length with increasing flexion angles, whereas grafts with more distal attachments increased in length with increasing flexion angles. The ALB and central single-bundle graft demonstrated a significant elongation from 0° to 120° of flexion (p < 0.001). The PMB decreased in length between 0° and 60° of flexion after which the bundle increased in length to its maximum length at 120° (p < 0.001). No significant differences in length changes were found between either the ALB or PMB and the central graft, and between the ALB and PMB at flexion angles ≥ 60° (n.s.). CONCLUSIONS: The most isometric attachment was proximal to the anatomic PCL footprint and resulted in non-physiological length changes. Moving the femoral attachment locations of the PCL significantly affected length change patterns, whereas moving the tibia locations did not. The importance of anatomically positioned (i.e., distal to the isometric area) femoral PCL reconstruction locations to replicate physiological length changes is highlighted. These data can be used to optimize tunnel positioning in either single- or double-bundle and primary or revision PCL reconstruction cases. LEVEL OF EVIDENCE: IV.

The Influence of Aspiration Volume on the Number of Osteoblastic Progenitors Obtained From Bone Marrow in Children.

BACKGROUND: Autologous bone marrow aspirates are utilized to treat various conditions in children. The biological value of bone marrow aspirate depends on the concentration of competent osteoblastic progenitors present in the aspirate. It has been shown in adults that increasing bone marrow aspiration volume beyond 2 mL decreases the concentration of osteoblast progenitor cells because of dilution of the sample with peripheral blood. The effect of varying bone marrow aspiration volumes on the osteoblast cell content has not been determined in children. METHODS: In total, 21 children (3 male and 18 female patients, age range 8 mo to 14 y) scheduled for pelvic osteotomy were included in the study. Three separate bone marrow aspirates of 1, 5, and 10 mL were obtained from the anterior superior iliac crest. Total number of nucleated cells was counted per aspirate and the prevalence of alkaline phosphatase-positive colony-forming units was determined per million nucleated cells. RESULTS: We measured a significant, proportional increase in the total number of nucleated bone marrow precursor cells between the 1 and 5 mL samples (mean±SD, 27±13 and 152±78 million nucleated cells, respectively; P<0.0001). When the aspiration volume doubled from 5 to 10 mL the total number of nucleated cells was 178±76 million (P=0.17). A proportional increase from 2214 alkaline phosphatase-positive colony-forming units in the 1 mL sample to 14,100 alkaline phosphatase-positive colony-forming units in the 5 mL sample was observed. However, the number of colony-forming units per aspirate decreased to 11,880 in the 10 mL sample. CONCLUSIONS: These data demonstrate that in children aspiration up to 5 mL bone marrow from the iliac crest yields a proportional increase in osteoblastic progenitor cells per aspirate. Increasing the aspiration volume beyond 5 mL results in hemodilution, rather than further selection of osteoblastic material. CLINICAL RELEVANCE: These data provide clinicians with a guideline for optimizing aspiration volume of bone marrow in children. LEVEL OF EVIDENCE: Level II-development of diagnostic criteria on basis of consecutive patients.

Symptomatic hallux valgus and dorsal bunion in adolescents with cerebral palsy: clinical and biomechanical factors.

AIM: The prevalence of severely symptomatic deformities of the first metatarsophalangeal (MTP) joint in adolescents with cerebral palsy (CP) requiring arthrodesis is unknown. Recent literature regarding these deformities is limited. We studied the presentation of severe, symptomatic deformities of the first ray in a large population of children and adolescents with CP and their association with gross motor function, CP subtype, and other musculoskeletal deformities. METHOD: We identified 41 patients with CP and a symptomatic deformity of the first MTP joint, managed by arthrodesis, from a large population based database over a 21-year period. Information recorded included demographics, CP subtype, Gross Motor Function Classification System (GMFCS), clinical presentation, and radiological features. RESULTS: Adolescents with spastic diplegia, at GMFCS levels II and III, were the most common group to develop symptomatic hallux valgus. In contrast, non-ambulant adolescents, at GMFCS levels IV and V, with dystonia or mixed tone, more commonly had dorsal bunions. INTERPRETATION: The type of first MTP joint deformity in patients with CP may be predicted by the type and distribution of movement disorder, and by GMFCS level. Specific patterns of associated musculoskeletal deformities may contribute to the development of these disorders and may provide a guide to surgical management. WHAT THIS PAPER ADDS: The prevalence of severe bunions requiring fusion surgery was 2%. The two types of bunion were hallux valgus and dorsal bunion. The type of bunion can be identified on both clinical and radiological grounds. The cerebral palsy subtype is predictive of the type of bunion.

An In Vivo Prediction of Anisometry and Strain in Anterior Cruciate Ligament Reconstruction - A Combined Magnetic Resonance and Dual Fluoroscopic Imaging Analysis.

PURPOSE: To evaluate the in vivo anisometry and strain of theoretical anterior cruciate ligament (ACL) grafts in the healthy knee using various socket locations on both the femur and tibia. METHODS: Eighteen healthy knees were imaged using magnetic resonance imaging and dual fluoroscopic imaging techniques during a step-up and sit-to-stand motion. The anisometry of the medial aspect of the lateral femoral condyle was mapped using 144 theoretical socket positions connected to an anteromedial, central, and posterolateral attachment site on the tibia. The 3-dimensional wrapping paths of each theoretical graft were measured. Comparisons were made between the anatomic, over the top (OTT), and most-isometric (isometric) femoral socket locations, as well as between tibial insertions. RESULTS: The area of least anisometry was found in the proximal-distal direction just posterior to the intercondylar notch. The most isometric attachment site was found midway on the Blumensaat line with approximately 2% and 6% strain during the step-up and sit-to-stand motion, respectively. Posterior femoral attachments resulted in decreased graft lengths with increasing flexion angles, whereas anterodistal attachments yielded increased lengths with increasing flexion angles. The anisometry of the anatomic, OTT and isometric grafts varied between tibial insertions (P < .001). The anatomic graft was significantly more anisometric than the OTT and isometric graft at deeper flexion angles (P < .001). CONCLUSIONS: An area of least anisometry was found in the proximal-distal direction just posterior to the intercondylar notch. ACL reconstruction at the isometric and OTT location resulted in nonanatomic graft behavior, which could overconstrain the knee at deeper flexion angles. Tibial location significantly affected graft strains for the anatomic, OTT, and isometric socket location. CLINICAL RELEVANCE: This study improves the knowledge on ACL anisometry and strain and helps surgeons to better understand the consequences of socket positioning during intra-articular ACL reconstruction.

In Vivo Anterolateral Ligament Length Change in the Healthy Knee During Functional Activities-A Combined Magnetic Resonance and Dual Fluoroscopic Imaging Analysis.

PURPOSE: To measure the in vivo anterolateral ligament (ALL) length change in healthy knees during step-up and sit-to-stand motions. METHODS: Eighteen healthy knees were imaged using magnetic resonance and dual fluoroscopic imaging techniques during a step-up and sit-to-stand motion. The ALL length change was measured using the shortest three-dimensional wrapping path, with its femoral attachment located slightly anterior-distal (ALL-Claes) or posterior-proximal (ALL-Kennedy) to the fibular collateral ligament attachment. The ALL length measured from the extended knee position of the non-weight-bearing magnetic resonance scan was used as a reference to normalize the length change. RESULTS: During the step-up motion (approximately 55° flexion to full extension), both the ALL-Claes and ALL-Kennedy showed a significant decrease in length of 21.2% (95% confidence interval 18.0-24.4, P < .001) and 24.3% (20.6-28.1, P < .001), respectively. During the sit-to-stand motion (approximately 90° flexion to full extension), both the ALL-Claes and ALL-Kennedy showed a consistent, significant decrease in length of 35.2% (28.8-42.2, P < .001) and 39.2% (32.4-46.0, P < .001), respectively. From approximately 90° to 70° of flexion, a decrease in length of approximately 6% was seen; 70° of flexion to full extension resulted in an approximately 30% decrease in length. CONCLUSIONS: The ALL was found to be a nonisometric structure during the step-up and sit-to-stand motion. The length of the ALL was approximately 35% longer at approximately 90° of knee flexion when compared with full extension and showed decreasing length at lower flexion angles. Similar ALL length change patterns were found with its femoral attachment located slightly anterior-distal or posterior-proximal to the fibular collateral ligament attachment. CLINICAL RELEVANCE: These data suggest that, if performing anatomic ALL reconstruction, graft fixation may be performed beyond 70° flexion to reduce the chance of lateral compartment overconstraint. Anatomic ALL reconstruction may affect the knee kinematics more in high flexion than at low flexion angles.

A lateral extra-articular tenodesis without additional hardware: Surgical technique and biomechanical comparison with an anatomic anterolateral ligament reconstruction in the augmentation of anterior cruciate ligament reconstruction.

BACKGROUND: The aims of this study were to describe a lateral extra-articular tenodesis (LET) using no additional hardware and compare the tibiofemoral kinematics of anterior cruciate ligament (ACL) reconstruction augmented with either the LET or a standard anatomic anterolateral ligament (ALL) reconstruction using intra-tunnel fixation. METHODS: Ten cadaveric knees were mounted on a robotic testing system and underwent a kinematic assessment of anterior tibial translation and internal tibial rotation under a simulated pivot-shift in the following states: ACL-intact, ACL-sectioned, ACL-sectioned/anterolateral complex (ALC)-sectioned, ACL-reconstructed/ALC-sectioned, ACL-reconstructed/ALL-reconstructed, and ACL-reconstructed/LET. For the LET, an iliotibial autograft was passed under the fibular collateral ligament and secured to the femur with the pull sutures of the ACL reconstruction femoral cortical suspensory fixation device, positioned at the distal ridge of Kaplan's fibers. RESULTS: Anterior tibial translation was restored to normal by ACL reconstruction without meaningful benefit of augmentation with LET or ALL. ACL reconstruction restored internal tibial rotation close to normal between 0° and 30°, but increased internal tibial rotation persisted between 45° and 90°. Augmentation of ACL reconstruction with the LET reduced internal rotation close to normal between 45° and 90°, whereas increased internal rotation persisted after ALL reconstruction. CONCLUSION: ACL reconstruction and LET are complementary in controlling tibiofemoral kinematics of knees with a combined ACL and ALC injury: ACL reconstruction restored native tibiofemoral kinematics except for internal rotation at flexion greater than 30°. The increased internal rotation at flexion greater than 30° was restored to normal with an LET, but not with an ALL reconstruction.

Management of Dorsal Bunion in Nonambulatory Adolescents with Cerebral Palsy: A Retrospective Cohort Study.

BACKGROUND: A dorsal bunion may occur in nonambulatory adolescents with cerebral palsy (CP) and a Gross Motor Function Classification System (GMFCS) level of IV or V. The deformity can cause pain, skin breakdown, and difficulty wearing shoes and braces. A consensus on the biomechanics and surgical management of dorsal bunions in persons with severe CP has not been established. METHODS: This retrospective cohort study included 23 nonambulatory adolescents with CP, GMFCS level IV or V, and symptomatic dorsal bunions requiring surgery. The median age at surgery was 17 years, and the median follow-up was 56 months. Reconstructive surgery included the excision of a 2 to 3-cm segment of the tibialis anterior tendon to correct the elevation of the first metatarsal. The fixed deformity of the first metatarsophalangeal joint was managed with use of corrective arthrodesis and dorsal plate fixation. Clinical and radiographic outcomes were assessed preoperatively and postoperatively at the transition to adult services. RESULTS: There were significant improvements in the clinical and radiographic outcome measures (p < 0.001). Pain was relieved, and there were no further episodes of skin breakdown. The elevation of the first metatarsal was corrected from a mean of 3° of dorsiflexion to a mean of 19° of plantar flexion. The deformity of the first metatarsophalangeal joint was corrected from a mean of 55° of plantar flexion to a mean of 21° of dorsiflexion. Six patients had complications, all of which were grade I or II according to the modified Clavien-Dindo system. CONCLUSIONS: The surgical reconstruction of a dorsal bunion via soft-tissue rebalancing of the first ray and corrective arthrodesis of the first metatarsophalangeal joint resulted in favorable medium-term clinical and radiographic outcomes in nonambulatory adolescents with CP. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Double-Bundle Anterior Cruciate Ligament Reconstruction With Primary Repair and Hamstring Autograft Augmentation.

The optimal treatment of a ruptured anterior cruciate ligament (ACL) restores the patient's native anatomy and biomechanics as close to normal as possible. The purpose of this technical note is to describe an ACL reconstruction technique in which a double-bundle concept is used, wherein one bundle contains repaired ACL tissue and the second bundle contains a hamstring autograft, and each bundle is tensioned independently. Even in chronic cases, this technique allows for incorporation of the native ACL because, more often than not, there is sufficient tissue of good quality available for repair of one bundle. By augmenting the ACL repair with an autograft sized to the fit the individual anatomy, the patient's ACL tibial footprint can be closely restored to normal, and the potential benefits of tissue preservation are combined with the biomechanical strengths of an autograft double-bundle ACL reconstruction.

Arthrodesis of the first metatarsophalangeal joint for severe hallux valgus in adolescents with cerebral palsy: A retrospective comparison study of three surgical techniques.

Purpose: We compared the outcomes of arthrodesis of the first metatarsophalangeal joint for severe hallux valgus in 31 adolescents with cerebral palsy, using three different methods of fixation: K-wires, non-locking plates, and locking plates. Methods: Clinical outcomes included time to weight-bearing, fusion rates and surgical complications. Radiographic assessment included comparing pre- and post-operative hallux valgus angles, intermetatarsal angles, interphalangeal angles, and lateral metatarsophalangeal angles. Patient-reported outcomes included pre- and post-operative visual analogue scales addressing bunion pain and concerns, difficulties with wearing shoes and braces, and difficulties with foot hygiene. Results: Of the 31 adolescents (16 male), 10 patients had K-wire fixation, 11 had a non-locking dorsal plate, and 10 had fixation with a dorsal locking plate. Mean age at surgery was 16 years (12-18 years) and mean follow-up was 4 years (2.7-6.5 years). Patients with K-wire fixation had delayed weight-bearing and had more complications than those managed by dorsal plating. There were significant improvements in radiographic parameters (except interphalangeal angle) and in patient-reported outcomes, in all groups (p < 0.001). However, radiographic and clinical outcomes were better in the dorsal plating groups compared to the K-wire group. Conclusion: Arthrodesis of the first metatarsophalangeal joint gave good correction of deformity with improvements in symptoms and radiographic parameters in adolescents with cerebral palsy. We recommend dorsal plating that allowed early weight-bearing and had fewer complications with better clinical and radiographic outcomes, than K-wire fixation. Level of evidence: IV: Retrospective case series.

Surgical technique: aperture fixation in PCL reconstruction: applying biomechanics to surgery.

BACKGROUND: Biomechanical studies suggest reducing the effective graft length during transtibial posterior cruciate ligament (PCL) reconstruction by augmenting the distal tibial fixation with a proximal screw near the tibial tunnel aperture could increase graft stiffness and provide a more stable reconstruction. However, it remains unknown to what extent this mechanical theory influences in vivo graft performance over time. SURGICAL TECHNIQUE: We developed a technique to augment tibial distal fixation with a proximal screw near the tibial tunnel aperture to shorten the effective graft length and increase graft stiffness. PATIENTS AND METHODS: We retrospectively reviewed all 10 patients who had isolated PCL reconstructions with combined distal and proximal tibial fixation from 2003 to 2007. Mean age of the patients was 36.5 years. We measured ROM and obtained Tegner, International Knee Documentation Committee (IKDC), and Lysholm scores. Anteroposterior stability was evaluated with a KT-2000 arthrometer. Minimum followup was 1 year (mean, 2.5 years; range, 1-4.8 years). RESULTS: Mean Tegner scores before injury and at last followup were 7.3 and 6.5, respectively. Mean postoperative IKDC score was 87 versus a preoperative IKDC score of 43. Mean Lysholm score was 89 at last followup. All patients achieved full terminal extension. No patient had greater than a 5-mm difference in anterior or posterior displacement from the contralateral knee as measured by a KT-2000 arthrometer postoperatively (0.93 ± 0.79 mm). CONCLUSIONS: In this small series, augmentation of tibial distal fixation with a proximal screw near the tibial tunnel aperture during reconstruction of the isolated PCL rupture restored function, motion, and stability. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Tunnel position and graft orientation in failed anterior cruciate ligament reconstruction: a clinical and imaging analysis.

PURPOSE: It has been reported that technical error in positioning the graft tunnel is the most common problem in anterior cruciate ligament (ACL) reconstruction. The objective of this study was to quantitatively evaluate femoral and tibial tunnel positions and intra-articular graft orientation of primary ACL reconstruction in patients who had undergone revision ACL reconstruction. We postulated that this patient cohort had a nonanatomically positioned tunnel and graft orientation. METHODS: Twenty-six patients who had undergone a revision ACL were investigated. Clinical magnetic resonance (MR) images prior to revision were analysed. Three-dimensional models of bones and tunnels on the femur and tibia were created. Intra-articular graft orientation was measured in axial, sagittal and coronal planes. Graft positions were measured on the tibial plateau as a percentage from anterior to posterior and medial to lateral; graft positions on the femur were measured using the quadrant method. RESULTS: Sagittal elevation angle for failed ACL reconstruction graft (69.6° ± 13.4°) was significantly greater (p < 0.05) than that of the native anteromedial (AM) and posterolateral (PL) bundles of the ACL (AM 56.2° ± 6.1°, PL 55.5° ± 8.1°). In the transverse plane, the deviation angle of the failed graft (37.3° ± 21.0°) was significantly greater than native ACL bundles. The tibial tunnel in this patient cohort was placed posteromedially and medially to the anatomical AM and PL bundles, respectively. The femoral tunnel was placed anteriorly to the anatomical AM and PL bundles. CONCLUSIONS: This study reveals that both the tibial and femoral tunnel positions and consequently the intra-articular graft orientation in this patient group with failed ACL reconstruction were nonanatomical when compared with native ACL values. The results can be used to improve tunnel placement in ACL reconstruction.

Estimation of in vivo ACL force changes in response to increased weightbearing.

Accurate knowledge of in vivo anterior cruciate ligament (ACL) forces is instrumental for understanding normal ACL function and improving surgical ACL reconstruction techniques. The objective of this study was to estimate the change in ACL forces under in vivo loading conditions using a noninvasive technique. A combination of magnetic resonance and dual fluoroscopic imaging system was used to determine ACL in vivo elongation during controlled weightbearing at discrete flexion angles, and a robotic testing system was utilized to determine the ACL force-elongation data in vitro. The in vivo ACL elongation data were mapped to the in vitro ACL force-elongation curve to estimate the change in in vivo ACL forces in response to full body weightbearing using a weighted mean statistical method. The data demonstrated that by assuming that there was no tension in the ACL under zero weightbearing, the changes in in vivo ACL force caused by full body weightbearing were 131.4 ± 16.8 N at 15 deg, 106.7 ± 11.2 N at 30 deg, and 34.6 ± 4.5 N at 45 deg of flexion. However, when the assumed tension in the ACL under zero weightbearing was over 20 N, the change in the estimated ACL force in response to the full body weightbearing approached an asymptotic value. With an assumed ACL tension of 40 N under zero weightbearing, the full body weight caused an ACL force increase in 202.7 ± 27.6 N at 15 deg, 184.9 ± 22.5 N at 30 deg, and 98.6 ± 11.7 N at 45 deg of flexion. The in vivo ACL forces were dependent on the flexion angle with higher force changes at low flexion angles. Under full body weightbearing, the ACL may experience less than 250 N. These data may provide a valuable insight into the biomechanical behavior of the ACL under in vivo loading conditions.

Application guidelines for dynamic knee joint analysis with a dual fluoroscopic imaging system.

The widespread availability of mobile digital fluoroscopic systems with dynamic imaging capabilities places this type of motion analysis within reach of many research groups. With the addition of the second fluoroscope though, and the incorporation of a treadmill to analyze gait, the fluoroscopic analysis technique, which was once a rather straightforward method, has become more complex. Therefore, the purpose of the present manuscript was to provide a comprehensive review of the various processes that are associated with the dynamic knee joint motion analysis, including patient selection, construction of three-dimensional knee models, fluoroscopic scanning, and matching.

[Anterior cruciate ligament rupture in children: A growing problem]. / Voorste-kruisbandruptuur bij kinderen.

The number of knee injuries in young children has risen sharply in recent years, due to more intensive participation in sporting activities by children at an increasingly lower age. This has led to more anterior cruciate ligament (ACL) ruptures. An ACL rupture has major consequences for the young athlete, but diagnosing this injury in a child can be difficult due to pain and anxiety. The criteria for appropriate treatment of an ACL rupture are not always clear for the child, the doctor, the parents and the sporting coach. Here we describe the diagnosis and possible treatment options for an ACL rupture in children based on three cases. We conclude that the incidence of ACL ruptures in children is a growing problem. There is a challenge for sports associations, sports clubs, trainers and parents to build in prevention programmes during weekly training sessions. The considerations to be taken into account concerning diagnosis and different treatment options show, once again, that children cannot simply be considered as small adults.

The Occurrence of Meniscal and Chondral Injury in Two-Stage Revision Anterior Cruciate Ligament Reconstruction: A Consecutive Case Series.

Two-stage revision anterior cruciate ligament (ACL) reconstruction is an effective way to revise suboptimal tunnel-placement allowing for proper graft fixation. However, prolonged increased laxity of the knee may increase the risk of meniscal or chondral injury. It was hypothesized that no additional meniscal or chondral lesions occur in between the two stages of the two-stage revision ACL reconstruction. In this retrospective study, 42 patients undergoing a two-stage revision ACL reconstruction were included. Surgical notes for both stages were screened for meniscal and chondral status, interventions to any concurrent injury, surgery dates, along with basic patient characteristics. In 4 of the 42 patients, a new meniscal tear occurred in between the two stages, of which three required partial meniscectomy during the second stage of the ACL revision. One patient experienced a new small degenerative tear that did not require intervention. Two out of the four menisci that were repaired during the first stage had failed and required partial meniscectomy. No significant difference was found in the time between the two stages with respect to the occurrence of meniscal tears. No significant differences in chondral status were found. In conclusion, approximately 10% of patients developed a new meniscal tear and no difference in macroscopic chondral injury was observed between the first and second stages.

The Medial Patellofemoral Ligament Is a Dynamic and Anisometric Structure: An In Vivo Study on Length Changes and Isometry.

BACKGROUND: Medial patellofemoral ligament (MPFL) reconstruction is associated with a high rate of complications, including recurrent instability and persistent knee pain. Technical errors are among the primary causes of these complications. Understanding the effect of adjusting patellofemoral attachments on length change patterns may help surgeons to optimize graft placement during MPFL reconstruction and to reduce graft failure rates. PURPOSE: To determine the in vivo length changes of the MPFL during dynamic, weightbearing motion and to map the isometry of the 3-dimensional wrapping paths from various attachments on the medial femoral epicondyle to the patella. STUDY DESIGN: Descriptive laboratory study. METHODS: Fifteen healthy participants were studied with a combined computed tomography and biplane fluoroscopic imaging technique during a lunge motion (full extension to ~110° of flexion). On the medial femoral epicondyle, 185 attachments were projected, including the anatomic MPFL footprint, which was divided into 5 attachments (central, proximal, distal, posterior, and anterior). The patellar MPFL area was divided into 3 possible attachments (proximal, central, and distal). The length changes of the shortest 3-dimensional wrapping paths of the various patellofemoral combinations were subsequently measured and mapped. RESULTS: For the 3 patellar attachments, the most isometric attachment, with an approximate 4% length change, was located posterior and proximal to the anatomic femoral MPFL attachment, close to the adductor tubercle. Attachments proximal and anterior to the isometric area resulted in increasing lengths with increasing knee flexion, whereas distal and posterior attachments caused decreasing lengths with increasing knee flexion. The anatomic MPFL was tightest in extension, decreased in length until approximately 30° of flexion, and then stayed near isometric for the remainder of the motion. Changing both the femoral and patellar attachments significantly affected the length changes of the anatomic MPFL ( P < .001 for both). CONCLUSION: The most isometric location for MPFL reconstruction was posterior and proximal to the anatomic femoral MPFL attachment. The anatomic MPFL is a dynamic, anisometric structure that was tight in extension and early flexion and near isometric beyond 30° of flexion. CLINICAL RELEVANCE: Proximal and anterior MPFL tunnel positioning should be avoided, and the importance of anatomic MPFL reconstruction is underscored with the results found in this study.

Validation of a non-invasive fluoroscopic imaging technique for the measurement of dynamic knee joint motion.

The accurate measurement of the in vivo knee joint kinematics in six degrees-of-freedom (6DOF) remains a challenge in biomedical engineering. We have adapted a dual fluoroscopic imaging system (DFIS) to investigate the various in vivo dynamic knee joint motions. This paper presents a thorough validation of the accuracy and repeatability of the DFIS system when used to measure 6DOF dynamic knee kinematics. First, the validation utilized standard geometric spheres made from different materials to demonstrate the capability of the DFIS technique to determine the object positions under changing speeds. The translational pose of the spheres could be recreated to less than 0.15+/-0.09 mm for velocities below 300 mm/s. Next, tantalum beads were inserted into the femur and tibia of two fresh frozen cadaver knees to compare the dynamic kinematics measured by matching knee models to the kinematics from the tantalum bead matching-a technique similar to Roentgen stereophotogrammetric analysis (RSA). Each cadaveric knee was attached to the crosshead of a tensile testing machine and vertically translated at a rate of 16.66 mm/s while images were captured with the DFIS. Subsequently, the tibia was held fixed and the femur manually flexed from full extension to 90 degrees of flexion, as the DFIS acquired images. In vitro translation of the cadaver knee using the tensile testing machine deviated from predicted values by 0.08+/-0.14 mm for the matched knee models. The difference between matching the knee and tantalum bead models during the dynamic flexion-extension motion of the knee was 0.1+/-0.65 degrees /s in flexion speed; 0.24+/-0.16 mm in posterior femoral translation; and 0.16+/-0.61 degrees in internal-external tibial rotation. Finally, we applied the method to investigate the knee kinematics of a living subject during a step ascent and treadmill gait. High repeatability was demonstrated for the in vivo application. Thus, the DFIS provides an easy and powerful tool for accurately determining 6DOF positions of the knee when performing daily functional activities.

The effect of ACL deficiency on the end-to-end distances of the tibiofemoral ACL attachment during in vivo dynamic activity.

PURPOSE: To evaluate the effect of ACL deficiency on the in vivo changes in end-to-end distances and to determine appropriate graft fixation angles for commonly used tunnel positions in contemporary ACL reconstruction techniques. METHODS: Twenty-one patients with unilateral ACL-deficient and intact contralateral knees were included. Each knee was studied using a combined magnetic resonance and dual fluoroscopic imaging technique while the patients performed a dynamic step-up motion (~50° of flexion to extension). The end-to-end distances of the centers of the anatomic anteromedial (AM), posterolateral (PL) and single-bundle ACL reconstruction (SB-anatomic) tunnel positions were simulated and analyzed. Comparisons were made between the elongation patterns between the intact and ACL-deficient knees. Additionally, a maximum graft length change of 6% was used to calculate the deepest flexion fixation angle. RESULTS: ACL-deficient knees had significantly longer graft lengths when compared with the intact knees for all studied tunnel positions (p < 0.01). The end-to-end distances for the AM, PL and SB-anatomic grafts were significantly longer between 0-30° of flexion when compared with the intact knee by p < 0.05 for all. Six percent length change occurred with fixation of the AM bundle at 30° of flexion, PL bundle at 10° and the SB-anatomic graft at 20°. CONCLUSIONS: ACL-deficient knees had significantly longer in vivo end-to-end distances between 0°-30° of flexion for grafts at the AM, PL and SB-anatomic tunnel positions when compared with the intact knees. Graft fixation angles of <30° for the AM, <10° for the PL, and <20° for the SB-anatomic grafts may prevent permanent graft stretch.